Neglects to mention that people who work in an occupation where they have an opportunity to get four cups of coffee a day are usually office or transport jobs.... not dangerous ones. Any thoughts?
I grew up in town where most people worked some sort of blue collar job, and I recall plenty of big coffee drinkers. I spent a summer working in a steel mill and it wasn't unusual to see guys arriving with large thermoses of coffee. Those that didn't bring it to work could purchase it from vending machines in the break rooms. A couple of cups before work, a couple during breaks or lunch, and by the end of the day they had had at least four cups of coffee.
I've noticed several design suggestions in your code.